The experiments proposed will clarify the role(s) of hormones in the activation of a behavior which is accessible to fairly complete analysis by intracellular recording from identified neurons. The behavior, ecdysis (shedding of the skin) in the cricket, is long-lasting and complex, but is composed of simpler, highly stereotyped subroutines (motor programs), which involve small numbers of neurons and can be studied individually. The proposal involves: (1) identification of motor and interneurons involved in one hormonally primed or triggered motor program, (2) characterization of the effects of hormones on these neurons, and (3) an analysis of the combined effects of hormones on interacting sets of neurons which correspond to single primed or triggered motor programs. Hormonal effects on resting potentials, input resistances, spike thresholds, pacemaker properties, synaptic function, and specific ionic permeabilities will be determined. This information will then be used to describe in detail the mechanisms underlying the priming and triggering actions of hormones on the cricket's ecdysial behavior.